System and method for discrete gain control in hybrid MIMO RF beamforming for multi layer MIMO base station

ABSTRACT

A multiple-input-multiple-output (MIMO) receiving system configured for receiving multiple transmission layers is provided herein. The system includes a plurality of beamformed tunable receiving antennas configured to receive a plurality of transmitted layers; and a control module configured to select for the beamformed antennas a single set of discrete weights for tuning said antennas for all of the transmitted layers so that the weights are selected for optimal performance of said receiving system, wherein said selection is carried out based on an extended Maximal Ratio Combining (MRC) metric or other quality metric measured by the MIMO baseband module, and using said measured metric separately for each beamformed antenna to determine gain or attenuation independently of phase selection.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 13/762,188, filed on Feb. 7, 2013, now U.S. Pat.No. 8,619,927, issued on Dec. 31, 2013, which is a continuation-in-partapplication of U.S. patent application Ser. No. 13/630,146 filed on Sep.28, 2012, now U.S. Pat. No. 8,654,883, issued on Feb. 18, 2014, whichclaims benefit from U.S. Provisional Patent Application Nos.: 61/652,743filed on May 29, 2012; 61/657,999 filed on Jun. 11, 2012; and 61/665,592filed on Jun. 28, 2012; U.S. patent application Ser. No. 13/762,188 alsoclaims benefit from U.S. Provisional Patent Application Nos.: 61/658,015filed on Jun. 11, 2012; 61/658,001 filed on Jun. 11, 2012; 61/658,004filed on Jun. 11, 2012; 61/665,590 filed on Jun. 28, 2012; 61/667,053filed on Jul. 2, 2012; and 61/665,605 filed on Jun. 28, 2012, all ofwhich are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to the field of radio frequency(RF) multiple-input-multiple-output (MIMO) systems and in particular tosystems and methods for enhanced performance of RF MIMO systems using RFbeamforming and/or digital signal processing.

BACKGROUND OF THE INVENTION

Prior to setting forth a short discussion of the related art, it may behelpful to set forth definitions of certain terms that will be usedhereinafter.

The term “MIMO” as used herein, is defined as the use of multipleantennas at both the transmitter and receiver to improve communicationperformance, where more than one radio, supported by digital signalprocessing are used. MIMO offers significant increases in datathroughput and link range without additional bandwidth or increasedtransmit power. It achieves this goal by spreading the transmit powerover or collecting the received signal from the antennas to achievespatial multiplexing that improves the spectral efficiency (more bitsper second per Hz of bandwidth) or to achieve a diversity gain thatimproves the link reliability (reduced fading), or increased antennadirectivity.

The term “beamforming” sometimes referred to as “spatial filtering” asused herein, is a signal processing technique used in antenna arrays fordirectional signal transmission or reception. This is achieved bycombining elements in the array in such a way that signals at particularangles experience constructive interference while others experiencedestructive interference. Beamforming can be used at both thetransmitting and receiving ends in order to achieve spatial selectivity.

The term “beamformer” as used herein refers to RF circuitry thatimplements beamforming and usually includes a combiner and may furtherinclude switches, controllable phase shifters, and in some casescontrollable amplifiers and/or controllable attenuators.

The term “layer” as used herein, or specifically, single layer isdefined as a transmitted signal carrying a data stream from a singletransmitting antenna. Multi-layer transmission is defined asco-frequency simultaneous multiple data streams radiated over multipleantennae using pre-coding that facilitates spatial separation, in a waythat allows the various co-frequency receivers each to receive their owndata stream while suppressing the others.

The term “Receiving Radio Distribution Network” or “Rx RDN” or simply“RDN” as used herein is defined as a group of beamformers as set forthabove.

The term “hybrid MIMO RDN” as used herein is defined as a MIMO systemthat employs two or more antennas per channel (N is the number ofchannels and M is the total number of antennas and M>N). Thisarchitecture employs a beamformer for each channel so that two or moreantennas are combined for each radio circuit that is connected to eachone of the channels.

The term “average” as used herein means summation of a series of Lvalues without necessarily dividing by the L, the result being subjectedto scaling or normalization.

In hybrid MIMO RDN receiving systems, when the phases of the receivedsignals from each antenna are properly adjusted with respect to oneanother, the individual signals may be passively combined and result inan improved Signal to Interference plus Noise Ratio (SINR) for thereceiving system. A drawback of passive combining schemes is that if theinput signals or noises have different powers, theses imbalances maysignificantly affect the SINR of the combined signal at the output ofthe combiner of the beamformer and may therefore degrade the gain of thebeamformer.

SUMMARY

Some embodiments of the present invention include a system and methodfor selectively and discretely amplifying or attenuating antennas in ahybrid multiple-input-multiple-output (MIMO) radio distribution network(RDN) receiving system. The system may include a MIMO receiving systemincluding a MIMO baseband module having N branches; an RDN connected tothe MIMO receiving system, the RDN comprised of at least one beamformerfed by (e.g., receives input from) two or more antennas, so that a totalnumber of antennas in the system is M, wherein M is greater than N,wherein each one of the beamformers include a passive combinerconfigured to combine signals coming or received from the antennascoupled to a respective beamformer into a combined signal, wherein theat least one beamformer is further configured to selectively amplify orattenuate in discrete values, one or more of the signals coming from theM antennas, based on one or more quality metrics measured by the MIMObaseband module.

Additional, and/or other aspects and/or advantages of the presentinvention are set forth in the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention and in order to show how itmay be implemented, references are made, purely by way of example, tothe accompanying drawings in which like numerals designate correspondingelements or sections. In the accompanying drawings:

FIG. 1 is a high level block diagram illustrating a system according toembodiments of the present invention;

FIG. 2 is a high level block diagram illustrating one aspect of a systemaccording to embodiments of the present invention;

FIG. 3 is a high level block diagram illustrating another aspect of asystem according to embodiments of the present invention;

FIG. 4 is a high level block diagram illustrating yet another aspect ofa system according to embodiments of the present invention;

FIGS. 5A and 5B to 9A and 9B are graph diagrams illustratingquantitative aspects according to some embodiments of the presentinvention;

FIG. 10 is a graph diagram illustrating yet another aspect according tosome embodiments of the present invention;

FIG. 11 is a high level flowchart illustrating a method according tosome embodiments of the present invention; and

FIG. 12 is a high level flowchart illustrating a method according tosome embodiments of the present invention.

The drawings together with the following detailed description make theembodiments of the invention apparent to those skilled in the art.

DETAILED DESCRIPTION

With specific reference now to the drawings in detail, it is stressedthat the particulars shown are for the purpose of example and solely fordiscussing the preferred embodiments of the present invention, and arepresented in the cause of providing what is believed to be the mostuseful and readily understood description of the principles andconceptual aspects of the invention. In this regard, no attempt is madeto show structural details of the invention in more detail than isnecessary for a fundamental understanding of the invention. Thedescription taken with the drawings makes apparent to those skilled inthe art how the several forms of the invention may be embodied inpractice.

It is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement of thecomponents set forth in the following descriptions or illustrated in thedrawings. The invention is applicable to other embodiments and may bepracticed or carried out in various ways. Also, it is to be understoodthat the phraseology and terminology employed herein is for the purposeof description and should not be regarded as limiting.

FIG. 1 is a high level block diagram illustrating a system according toembodiments of the present invention. System 100 includes a MIMOreceiving system set in a hybrid MIMO RDN configuration. In the hybridMIMO RDN configuration, baseband module 120 receives (e.g., receives oraccepts inputs from) N branches and is configured to operate, on thebaseband level, in accordance with any known or legacy MIMO receivingscheme. System 100 further includes a radio distribution network 110(RDN) connected to baseband module 120 via radio circuits 12-1 to 12-N.RDN 110 includes at least one beamformer with antenna amplification orattenuation functionality such as 140-1 and 140-N, being fed by (e.g.,receiving or accepting inputs from) two or more antennas such as 10-1-1to 10-1-K₁ through 10-N-1 to 10-N-K_(N), so that a total number ofantennas in system 100 is M=K₁+K₂+ . . . +K_(N), wherein M is an integergreater than N, also an integer. Additionally, each one of thebeamformers includes a combiner (not shown here) configured to combinesignals received or coming from the antennas into a single combinedsignal converted to baseband by radio module 12-1 to 12-N. Basebandmodule 120 further includes an RF control module 130 being configured totune RDN 110, for example by adjusting phase shifters located withinbeamformers 140-1 to 140-N. System 100 includes a beamformer withantenna selective discrete amplification/attenuation such as 140-1 to140-N for each group of antennas such as 10-1-1 to 10-1-K₁ through10-N-1 to 10-N-K_(N) that is being combined into a single radio circuitsuch as 12-1 to 12-N. In operation, any of beamformers 140-1 to 140-N isconfigured to selectively amplify or attenuate one or more signalscoming from the antennas 10-1-1 to 10-1-K₁ through 10-N-1 to 10-N-K_(N)respectively which are combined and feed the respective radio circuits12-1 to 12-N. The amplification or attenuation may be carried out indiscrete steps as will be described hereinafter, and the decision whichantenna(s) to amplify or attenuate and at what value is carried out atthe RF control module 130 in operative association with baseband module120. As will be explained below, there are many embodiments that may beused in order to implement the selective and discreteamplification/attenuation procedure. Control module 130 may be forexample a general purpose processor executing software or code, or maybe a dedicated processor.

FIG. 2 is a high level block diagram illustrating one aspect of a systemaccording to embodiments of the present invention. System 200 shows apossible implementation in which the selective amplification is carriedout by using a low noise amplifier (LNA) module such as 220-1-1 to220-1-K₁, each connected to or associated with a different respectiveantenna of 10-1-1 to 10-1-K₁ followed by a respective phase shifter210-1-1 to 210-1-K₁ that are used by the control module (shown inFIG. 1) to tune the phase of antennas 10-1-1 to 10-1-K₁. LNA modules220-1-1 to 220-1-K₁ are controlled by the control module of the basebandmodule by applying discrete levels of gains which are selected on an adhoc basis for each one of the antenna signals. Control module 130 may beconfigured to select for the beamformed antennas a single set of weightsfor tuning the antennas for all of the transmitted layers so that theweights are selected for optimal performance. More specifically, asingle set of weights is used to determine the gain/attenuation valuesfor the different antennas of the beamformer (each antenna is associatedwith its own weight). The single set is required to yield the bestperformance for all layers transmitted (e.g., the weight remains thesame for all layers) hence the challenge is to find weights thatoptimize the performance of all layers.

According to some embodiments of the present invention, the discretelevels may include maximum gain and “off”. Alternatively, the discretelevels include maximum gain, one or more intermediate gain levels, and“off”. In a case that the internal noise dominates the signal and thelevel of the respective signal is below a specific threshold, the radiofrequency (RF) control module may apply the discrete level “off” to aspecific signal coming from the antennas.

FIG. 3 is a high level block diagram illustrating another aspect of asystem according to embodiments of the present invention. Specifically,a possible implementation of the aforementioned LNA module 220 isdescribed. LNA module 220 may include a multiband controllable filter310. An LNA 320 is followed by a step attenuator 330. The keyrequirement of LNA module 220 is that the overall gain must be highenough to establish the system noise temperature in the presence of thefollowing cascaded circuit gains and losses. Additionally, LNA module220 must provide a means to reduce gain to the signal and to itsself-generated noise simultaneously. This may be accomplished byproviding a continuous control of LNA 320 gain or through discrete gaincontrol by means of step attenuator 330 as shown. The implementation ofLNA module 220 may take many forms as may be apparent to anyone skilledin the field of RF circuit design and the effect of cascaded gains andlosses to system noise temperature performance. It is noted that in thisembodiment, a large number of multiband controllable filters 310 may berequired making this embodiment relatively expensive.

FIG. 4 depicts a passive embodiment that avoids using LNA and LNAfilters and is suitable for example when external noise is the dominantnoise source. Antenna 10-1-1 (being one of many—not shown) is connectedvia a switch 410 to a phase shifter 420-1 which is connected to aselection switch 430 which is connected to another selection switch 470via a short circuit 440, a pad 450 with a predefined attenuation valueand an open circuit 460A, 460B. Switch 470 is then connected to acombiner 480 fed by similar circuits of other antennas (not shown). Theoutput of combiner 480 is then connected to a selection switch 490before going to or providing output to the radio circuit and thebaseband module (not shown here).

In some embodiments, the number of discrete values of attenuation isonly two, in which case either pad 450 or the open circuit is removedand switches 430 and 470 are replaced with single pole double throw(SPDT) switches. In some other embodiments, the number of discretevalues of attenuation is greater than three, in which case additionalpads of different values are added and switches 430 and 470 are expandedaccordingly. The aforementioned ternary architecture that allows threedifferent values for the step attenuator (e.g., short circuit, pad, opencircuit) provides a cost effective manner of changing the amplitude ofthe signals coming from the antennas in hybrid MIMO RDN architecture.The use of a pad provides an advantage over the more simple solution ofmerely connecting and disconnecting an antenna (the binary embodiment)by providing a better gain (and average SINR) as will be demonstratedbelow. A threshold approach may be adopted in operating the stepattenuator. Specifically, switching between the possible attenuationvalues is mapped to specified metric values, m_(i), defined for each ithantenna in the beamformer. The mapping between m_(i) and the attenuationvalues may be carried out for example by comparing m_(i) to thresholds.Note that MRC (Maximal Ratio Combining) is a metric defined forcombining a single layer's transmission by multiple antennas, as theratio between the root mean square (RMS) signal value and the meansquare noise level. Embodiments of the invention describe a metric whichis an expansion of this concept, where two or more layers transmitted,typically having different magnitudes and phases, are combined bymultiple antennas to create—by nature—a suboptimal result, as it seekssuch a single weights setting (e.g., a single set of weights) that bestfits all layers contribution. Although it is impossible to find a singleset of weights that maximizes performance for all layers, it is possibleto find such a single set of weights that optimizes a combined layercontribution to the SINR value.

A possible metric for determining signal attenuation may be derived foreach antenna by calculating an average magnitude of the signal layersreceived by an antenna and dividing the average by the noise power forthe same antenna, where the average may be a voltage average or a squareroot of a power average of the individual layers received by theantenna.

The first variant of the proposed metric, using voltage averaging, maybe calculated as in the non-limiting example of Eq. (1) below:

$\begin{matrix}{m_{i} = \frac{\sum\limits_{j = 1}^{P}{\sum\limits_{k = 1}^{L}s_{i,j,k}}}{V_{i}}} & (1)\end{matrix}$

The second variant of the proposed metric, using square root of poweraveraging, may be calculated as described herein in Eq. (2) below:

$\begin{matrix}{m_{i} = \frac{\sqrt{\sum\limits_{j = 1}^{P}{\sum\limits_{k = 1}^{L}\left( s_{i,j,k} \right)^{2}}}}{V_{i}}} & (2)\end{matrix}$

In Eqs. (1) and (2) P is the number of transmitting antennas (layers), Lis the number of subcarrier frequencies, s_(i,j,k) is the amplitude ofthe layer j signal received by antenna i at frequency k, and V_(i) isthe noise power for antenna i. In some embodiments, s_(i,j,k) may be theamplitude of the channel from transmit antenna j to receive antenna i atfrequency k. Both variants of metric m_(i) are denoted herein by“extended MRC metric”. Other or different metrics may be used.

In some embodiments, for example when equal noise level (or interferencelevel) is assumed for all antennas, the metric may be simply the RMSsignal value (or for MIMO the sum of the RMS values of all signalstreams) or the SINR. The metric may normalize to the strongest antennasignal to a maximum of 1 (i.e., 0 dB reference level), and all othersare normalized by the same factor. The metric is compared to one or morethresholds—one threshold for two attenuation steps, two thresholds forthree attenuation steps, etc. It should be noted that this thresholdapproach may be applied to other embodiments such as the embodiment ofFIG. 3.

As the gain control may vary between zero, disconnected, and anintermediate value, selection amongst these requires more than onethreshold, for example, with one intermediate pre-determined value, afirst threshold, and a second threshold are used, and so when ExtendedMRC metric for a given antenna is below the first threshold, the antennais disconnected, when it is between the first and the second thresholds,the intermediate value is selected, and when said metric is above highthreshold, the antenna is connected without attenuation or gain.

In some embodiments, a controllable bypass 495 may connect switch 410with selection switch 490 so that combiner 480 is occasionally bypassed.Combiner bypass is desirable in a case that the SINR of all but oneantenna in a specific beamformer is worse than the SINR of the bestantenna in the beamformer. In that case, the control module isconfigured to bypass the combiner for the best antenna or attenuate therest of the antennas. In the cases where the decision is to disconnectall but one antenna as described, the signal can be routed to the radiovia path 495 to avoid the combiner losses of 480 thus providing astronger signal to the radio.

FIGS. 5A and 5B are graph diagrams illustrating a quantitative aspectaccording to some embodiments of the present invention. These figuresshow the diversity gain of a two antenna system, defined as the Signalto Noise Ratio (SNR) or SINR improvement of the two antenna system oversingle antenna, for various signal and noise power levels. In FIG. 5A itis assumed that internal noise dominates, therefore the noise for bothantennas have the same power, and the SNR difference between theantennas (the x axis) is due only to signal imbalance. The three curvesshown are for three different levels of attenuation applied to one ofthe antennas: 0 dB, 3 dB and antenna OFF. For 0 dB attenuation, as theSNR difference between the antennas varies from 0 dB to 30 dB, thediversity gain drops from +3 dB when the two input signals (SNR) areequal to almost −3 dB when the weak signal is 30 dB below the stronger.For 3 dB attenuation, the diversity gain is slightly reduced when thetwo input signals are equal and drops to almost −2 dB for 30 dB SNRdifference. With one of the antennas disconnected, the input SNR will beunchanged (i.e., 0 dB gain) as shown by the gain OFF trace. In someembodiments, if the Ohmic and leakage losses in the combiner areneglected, the weak signal should be disconnected at signal ratios ofapproximately between −6 dB and −10 dB. For signal ratios closer to eachother, the weak signal will still contribute positively to the systemperformance. In FIG. 5B it is assumed that external noise dominates sothat the two antenna signals are held constant and only the noise powervaries. The conclusions for both cases, internal or external noise, aresimilar.

FIGS. 6A and 6B through FIGS. 9A and 9B show that a similar analysisapplies to the case where more antennas are combined. Specifically, wheninternal noise dominates the signal it is illustrated how the diversitygain is reduced by signal imbalance for various numbers of weak signals.It is assumed here that all strong antennas are equal and all weak onesare equal. A ‘strong’ antenna as referred herein is an antenna which isthe reference vis-à-vis either signal level or SINR; a ‘weak’ antenna isone that is lower than the reference by either signal level or SINR. Ineach case it is shown how the diversity gain varies betweenapproximately +7 dB when all signals are equal to negative gain whensome are weaker. It can be seen in each chart that disconnecting theweak antennas is a better choice as the weak signal levels fall below athreshold level (around −6 to −10 dB for these cases). Similarconclusions apply when external noise dominates. In that case theassumption is that all antennas have equal signal power and only thenoise power varies, being equal for the best antennas, and also equalbut higher for the “low” antennas.

By looking at FIGS. 6A and 6B through FIGS. 9A and 9B it is possible tocalculate the optimal single pad value to be used for discrete MRC. Itis assumed the passive solution when each antenna can be combined,disconnected, or fed through a pad. As will be shown below, embodimentsof the invention describe that a single value for a pad can be selectedfor any number of antennas so that the SNR of the combined signal isoptimized. Referring back to FIG. 9A, when all five antennas' SNR areequal, the boundary gain is 7 dB. When three of them are much weakerthan some −8 dB, then they will be disconnected, if a pad option doesnot exist (binary embodiment). An example of selecting a 6 dB PAD forall three weak antennas is demonstrated below, of course assuming forthe sake of this chart that all strong ones are equal and all weak onesare equal. As can be seen, the gain curve with such 6 dB PADs crossesthe no-pad curve around −3 dB of SNR difference so kicking in the PADswill be done there. Also evident is that that curve crosses the x axisfurther, at some −12 dB of SNR difference (rather than −8 dB), thus theweak antennas disconnection are preferably done at that point.

The following is an example addressing the challenge of optimizing thepad value for this case, as well as the general case, with definitionsset forth below:

K: number of antennas being passively combined

s_(i): signal amplitude for antenna i, i=1,2 . . . K

V_(i): noise power for antenna i, i=1,2 . . . K

c_(i): linear multiplier (amplitude attenuator) for antenna i, i=1,2 . .. K

S: set of discrete multiplier values

Assuming S=[0, α, 1], the objective is to optimize α. To this end,define a signal to noise ratio SNR of the combined signal as in Eq. (3):

$\begin{matrix}{{SNR} = \frac{\left( {\sum\limits_{i = 1}^{K}{c_{i}s_{i}}} \right)^{2}}{\sum\limits_{i = 1}^{K}{c_{i}^{2}V_{i}^{2}}}} & {{Eq}.\mspace{14mu}(3)}\end{matrix}$

For any given set of amplitudes s_(i), there is a set of multipliersc_(i) εS that maximizes SNR:

$\begin{matrix}{{SNR}_{\max} = {\max\limits_{c_{i} \in S}{SNR}}} & {{Eq}.\mspace{14mu}(4)}\end{matrix}$

Since SNR_(max) depends on α, an optimization criterion is to choose αthat maximizes E{SNR_(max)} assuming a Rayleigh distribution foramplitudes s_(i).

FIG. 10 is a graph which illustrates numerically the variousexpectations of SNR_(max), or average SNR of the combined signal,resulting from possible selections of pad attenuation (in the graph padattenuation is 20 log₁₀(α)) assuming equal noise power for all antennas(V_(i)=1) and Rayleigh amplitudes. The averages are normalized withrespect to α=1 or 0 dB pad. The five different curves in chart 1000correspond to number of antennas from two to six. As can be noted, fortwo antennas, adding the pad increases the expectation by about 0.2 dBversus no pad (α=1). For six antennas the increase is about 0.4 dB. Ascan be seen, the peak gain for any number of antennas can be achieved byselection of 6.6 dB as a pad—as indicated by line 1010. Using this valueis advantageous in implementing a uniform solution for designing padsfor reducing to practice embodiments of the present invention. Forunequal noise powers, the optimal pad attenuation will be higher than6.6 dB, however little degradation in performance is observed if a 6.6dB pad is also used for unequal noise powers. Alternatively, a higherattenuation of, for example, 8 dB could be used for all cases. Othervalues and numbers of antennas may be used.

FIG. 11 is a high level flowchart illustrating a method 1100 accordingto some embodiments of the present invention. It is understood thatmethod 1100 may be implemented by any architecture and should not belimited to the aforementioned exemplary embodiments illustrated above.Method 1100 includes for example: receivingmultiple-input-multiple-output (MIMO) radio frequency (RF) signals via Mantennas 1110; selectively amplifying or attenuating in discrete steps,one or more of the signals coming from the M antennas 1120; passivelycombining the amplified or attenuated signals into N combined signals,wherein M is greater than N 1130; and conveying or providing the Ncombined signals to a MIMO baseband module having N branches 1140.Additionally, stage 1120 of selectively amplifying or attenuating iscarried out based on one or more specified quality metrics measured bythe MIMO baseband module.

According to some embodiments, the selection of the set of weights maybe carried out based on an extended MRC metric as expressed in Eqs. (1)and (2) and using the extended MRC metric separately (i.e., by ignoringthe contribution of other antennas) for each beamformed antenna todetermine gain or attenuation independently of phase selection (i.e.,the gain selection and the phase selection may be carried out withoutaffecting each other's selection process).

FIG. 12 is a high level flowchart illustrating a method 1200 accordingto some embodiments of the present invention. It is understood thatmethod 1200 may be implemented by any architecture and should not belimited to the aforementioned exemplary embodiments illustrated above.Method 1200 may include receiving a plurality of transmitted layers viaa plurality of beamformed tunable receiving antennas configured toreceive a plurality of transmitted layers 1210; selecting for thebeamformed antennas a single set of weights for tuning the antennas forall of the transmitted layers so that the weights are selected foroptimal performance, wherein said selection is carried out based on anextended MRC metric 1230; and providing or transferring possibly via RFwaveguides the beamformed signals to a multiple-input-multiple-output(MIMO) receiving system 1220.

As will be appreciated by one skilled in the art, aspects of the presentinvention may be embodied as a system, method or an apparatus.Accordingly, aspects of the present invention may take the form of anentirely hardware embodiment, an entirely software embodiment (includingfirmware, resident software, micro-code, etc.) or an embodimentcombining software and hardware aspects that may all generally bereferred to herein as a “circuit,” “module” or “system.”

The aforementioned flowcharts and block diagrams illustrate thearchitecture, functionality, and operation of possible implementationsof systems and methods according to various embodiments of the presentinvention. In this regard, each block in the flowchart or block diagramsmay represent a module, segment, or portion of code, which comprises oneor more executable instructions for implementing the specified logicalfunction(s). It should also be noted that, in some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

In the above description, an embodiment is an example or implementationof the inventions. The various appearances of “one embodiment,” “anembodiment” or “some embodiments” do not necessarily all refer to thesame embodiments.

Although various features of the invention may be described in thecontext of a single embodiment, the features may also be providedseparately or in any suitable combination. Conversely, although theinvention may be described herein in the context of separate embodimentsfor clarity, the invention may also be implemented in a singleembodiment.

Reference in the specification to “some embodiments”, “an embodiment”,“one embodiment” or “other embodiments” means that a particular feature,structure, or characteristic described in connection with theembodiments is included in at least some embodiments, but notnecessarily all embodiments, of the inventions.

It is to be understood that the phraseology and terminology employedherein is not to be construed as limiting and are for descriptivepurpose only.

The principles and uses of the teachings of the present invention may bebetter understood with reference to the accompanying description,figures and examples.

It is to be understood that the details set forth herein do not construea limitation to an application of the invention.

Furthermore, it is to be understood that the invention can be carriedout or practiced in various ways and that the invention can beimplemented in embodiments other than the ones outlined in thedescription above.

It is to be understood that the terms “including”, “comprising”,“consisting” and grammatical variants thereof do not preclude theaddition of one or more components, features, steps, or integers orgroups thereof and that the terms are to be construed as specifyingcomponents, features, steps or integers.

If the specification or claims refer to “an additional” element, thatdoes not preclude there being more than one of the additional element.

It is to be understood that where the claims or specification refer to“a” or “an” element, such reference is not be construed that there isonly one of that element.

It is to be understood that where the specification states that acomponent, feature, structure, or characteristic “may”, “might”, “can”or “could” be included, that particular component, feature, structure,or characteristic is not required to be included.

Where applicable, although state diagrams, flow diagrams or both may beused to describe embodiments, the invention is not limited to thosediagrams or to the corresponding descriptions. For example, flow neednot move through each illustrated box or state, or in exactly the sameorder as illustrated and described.

The term “method” may refer to manners, means, techniques and proceduresfor accomplishing a given task including, but not limited to, thosemanners, means, techniques and procedures either known to, or readilydeveloped from known manners, means, techniques and procedures bypractitioners of the art to which the invention belongs.

The descriptions, examples, methods and materials presented in theclaims and the specification are not to be construed as limiting butrather as illustrative only.

Meanings of technical and scientific terms used herein are to becommonly understood as by one of ordinary skill in the art to which theinvention belongs, unless otherwise defined.

The present invention may be implemented in the testing or practice withmethods and materials equivalent or similar to those described herein.

While the invention has been described with respect to a limited numberof embodiments, these should not be construed as limitations on thescope of the invention, but rather as exemplifications of some of thepreferred embodiments. Other possible variations, modifications, andapplications are also within the scope of the invention. Accordingly,the scope of the invention should not be limited by what has thus farbeen described, but by the appended claims and their legal equivalents.

The invention claimed is:
 1. A system comprising: a multiple-input-multiple-output (MIMO) receiving system; a plurality of beamforming tunable receiving antennas configured to receive a plurality of transmitted layers; a MIMO baseband module; and a control module configured to select for the beamforming antennas a single set of discrete weights for tuning said antennas for all of the transmitted layers, wherein said selection is carried out based on a predefined quality metric, being an extended Maximal Ratio Combining (MRC) metric, measured by the MIMO baseband module for each antenna, and using average of various signals measured separately for each antenna to determine gain or attenuation independently of phase selection.
 2. The system according to claim 1, wherein said gain or attenuation is carried out by mapping the quality metric measured for each antenna by the MIMO baseband control module to discrete values of gain or attenuation.
 3. The system according to claim 1, wherein the quality metric for each antenna is derived by calculating an average magnitude of the signal layers received by an antenna and dividing the average by the noise power for the same antenna, wherein said average is a voltage average or a square root of a power average of the individual layers received by the antenna, wherein the metric is further normalized to a maximum value.
 4. The system according to claim 1, wherein in a case that the measured metric being extended MRC metric of some of the antennas in a specific beamformer is smaller than a first threshold, the control module is configured to selectively disconnect said antennas.
 5. The system according to claim 4, wherein in a case that the measured metric being the extended MRC metric of some of the antennas in a specific beamformer is larger than said threshold, but lower than a certain other threshold, the control module is configured to selectively attenuate said antennas using predetermined attenuators.
 6. The system according to claim 1, wherein the control module controls a plurality of gain controlled low noise amplifiers (LNA), each one of the LNA being associated with a different antenna.
 7. The system according to claim 1, wherein the MIMO baseband module is configured to measure a signal level and signal to interference plus noise ratio (SINR) of each signal coming from the antennas, and wherein the gain or attenuation is based on a measured signal level and SINR of each signal coming from the antennas.
 8. The system according to claim 2, wherein the discrete values include maximum gain and “off”.
 9. The system according to claim 2, wherein the discrete values include maximum gain, one or more intermediate gain levels, and “off”.
 10. The system according to claim 2, wherein in a case that the internal noise dominates and the level of the respective signal is below a specific threshold, the gain control module applies the discrete level “off” to a specific signal coming from the antennas.
 11. The system according to claim 2, further comprising at least one combiner connected to at least some of the beamforming antennas, wherein in a case that the measured metric of all but one of the antennas in a specific beamformer is worse than the metric for a specific antenna in the beamformer, the control module is configured to bypass the combiner for the specific antenna or attenuate the other the antennas based on a threshold.
 12. The system according to claim 2, wherein in a case that the measured metric being the extended MRC metric of some of the antennas in a specific beamformer is worse than the metric for a specific antenna in the beamformer, the control module is configured to selectively attenuate the weak antenna based on a threshold.
 13. The system according to claim 2, wherein in a case that the measured metric being the extended MRC metric of some of the antennas in a specific beamformer is worse than the metric for a specific antenna in the beamformer, the control module is configured to selectively disconnect the weak antenna based on a threshold.
 14. The system according to claim 2, wherein the control module sets a plurality of cascaded units each comprising a multiband controllable filter, a low noise amplifier, and a step attenuator, wherein each cascaded unit controls the gain of a different antenna signal.
 15. The system according to claim 1, wherein the control module controls discrete levels of attenuation.
 16. The system according to claim 15, wherein the discrete levels include maximum attenuation and an intermediate attenuation level.
 17. The system according to claim 15, wherein the control module sets a discrete level maximal attenuation to a specific signal coming from the antennas, in a case that a measured SINR of a respective signal is below a specific threshold.
 18. The system according to claim 15, wherein the control module sets a plurality of discrete levels attenuator configured to select between a connector, a pad having a specific attenuation level, and a disconnection, wherein each discrete levels attenuator controls the attenuation of a different antenna signal.
 19. A method comprising: receiving a plurality of transmitted layers via a plurality of beamforming tunable receiving antennas configured to receive a plurality of transmitted layers; selecting for the beamforming antennas a single set of weights for tuning said antennas for all of the transmitted layers, wherein said selection is carried out based on an extended Maximal Ratio Combining (MRC) metric measured separately for each antenna using average of various signals received by each antenna and using said extended MRC metric to determine gain or attenuation of the antennas independently of phase selection; and transferring the beamformed signals to a multiple-input-multiple-output (MIMO) receiving system.
 20. The method according to claim 19, wherein said gain or attenuation is carried out by mapping the quality metric measured for each antenna by the MIMO baseband control module to discrete values of gain or attenuation.
 21. The method according to claim 19, wherein the quality metric for each antenna is derived by calculating an average magnitude of the signal layers received by an antenna and dividing the average by the noise power for the same antenna, wherein said average is a voltage average or a square root of a power average of the individual layers received by the antenna, wherein the metric is further normalized to a maximum value.
 22. The method according to claim 19, wherein in a case that the measured metric being extended MRC metric of some of the antennas in a specific beamformer is smaller than a first threshold metric, the control module is configured to selectively disconnect said antennas.
 23. The method according to claim 22, wherein in a case that the measured metric being the extended MRC metric of some of the antennas in a specific beamformer is larger than said threshold metric, but lower than a certain other threshold, the control module is configured to selectively attenuate said antennas using predetermined attenuators.
 24. The method according to claim 19, further comprising controlling a plurality of gain controlled low noise amplifiers (LNA), each one of the LNA being associated with a different antenna.
 25. The method according to claim 19, further comprising measuring a signal level and signal to interference plus noise ratio (SINR) of each signal coming from the antennas, and wherein the amplifying or the attenuating is based on the measured signal level and SINR of each signal coming from the antennas. 